Here is the link to a great despill tutorial which goes over blending BG colors using the difference matte of a despilled plate –> to the original plate. If you are new to the concept of blending your despill with the background then you are really going to like this video. He talks about flame in the beginning of the video and switches to nuke later.

Thanks for watching, next I’ll go over how to achieve and control the despill to get what you need.